Pediatric bipolar disorder (PBD) is one of the most debilitating of all childhood psychiatric illnesses. Though comorbid anxiety is highly prevalent and worsens impairment, it is unknown the extent to which anxiety alters the neural functioning of PBD children. The current study seeks to identify the behavioral and neural deficits which are distinct to PBD with and without comorbid anxiety. This K22 Career Transition Award will enable me to gain training so that I may be an independent clinical neuroimaging researcher. My long-term goal is to elucidate the pathophysiology of PBD at it relates to core impairments. I hope to use this information to identify neural and behavioral markers for children at-risk for developing PBD. v The specific aims for this proposal are to: 1) Identify face-emotion classification biases in PBD youth, irrespective of anxiety. These deficits will differentiate PBD youth from those with anxiety only (ANX) and no disorder;2) Identify the neural correlates of PBD, with or without comorbid anxiety, when processing faces. The specific nature of these correlates will differentiate youth with PBD+ANX from those with PBD-ANX, ANX, and controls. To accomplish these aims, I will use a functional magnetic resonance neuroimaging (fMRI) task efface processing. Participants will view angry, scared, happy, and neutral faces and perform emotional and non-emotional ratings. Ratings and reaction time will allow for a group comparison of behavioral and cognitive functioning in response to different faces. Simultaneously, neural activation data will be collected to provide a measure of brain functioning and allow for a group comparison of activity in brain regions that process emotional information and regulate mood and behavior responses. In sum, this study will support the identification of behavior and brain deficits in youth with PBD when they view emotional stimuli. It will also clarify how co-occurring anxiety changes these deficits. Finally, it will begin to identify shared and divergent patterns of neural function in two prominent childhood mood psychopathologies. The relevance of this study is it has the potential to greatly improve our understanding of a highly debilitating childhood psychiatric illness. This information can then aid in the development of behavioral and neural markers to be used to identify children at-risk for PBD, thus greatly improving the quality of life of children with PBD and their families.